What is a Sulcus?

In anatomy, a sulcus is a fold, fissure, or crack. These structures can be found throughout the body, serving a number of different functions, but the most recognizable sulci are located in the brain. They make up the distinctive pattern of folds in the brain that increase its surface area, along with the gyri, the ridges in the brain. Many animals have ridged brains with a sulcus and gyrus pattern, allowing their heads to stay relatively small while their brains expand surface area and functional capacity.

The pattern of grooves on every brain is slightly different. Several large sulci tend to be fairly consistent across all members of a species and may be named and used by people examining the brain to orient themselves. In humans, for example, the lateral sulcus divides the frontal and parietal lobes from the temporal lobe, while the central sulcus runs between the parietal and frontal lobes. These grooves in the brain are used as landmarks to help people identify specific regions of interest in the brain.

Within a sulcus, brain cells are packed closely together along the sides of the groove. The cerebral cortex, wrapping around the surface of the brain, follows the gyri and sulci, with around two thirds of the cerebral cortex in humans being found between the folds of the brain. The brain cells are involved in the interpretation of touch and other sensory inputs, and the expanded surface area created by the folds allows an animal to have a larger cerebral cortex than it would otherwise. Animals with folded brains tend to be more advanced than those with flat or relatively unwrinkled brains.

Anatomists have been interested in the distinctive pattern of folds in the brain for centuries. Early anatomists drew the results of autopsies and brain examinations, and a number identified specific recurrent anatomical features in the brain, naming them for reference. As understanding of brain function has improved, the nomenclature surrounding various structures has also grown more precise and more detailed.

Research on the brain has allowed people to identify activity in various regions of the brain. This provides information about how brain functions under normal conditions and what happens when areas of the brain are damaged. It is sometimes possible for brains to essentially rewire themselves to make up for areas of damage, while in other cases, cognitive function can be permanently impaired by strokes, trauma, and other injuries to the brain.